The compounds having a fluoroalkyl group are useful as various chemical products (for example, pharmaceuticals, agricultural chemicals, electronic materials and so on) and production intermediates thereof.
In order to produce the compounds having a fluoroalkyl group, fluoroalkylation reactions and fluoroalkylating agents have been developed heretofore. The fluoroalkylation reaction is a reaction by which a fluoroalkyl group is introduced into a starting compound (a material compound) which is an organic compound. In other words, the fluoroalkylation reaction is a reaction which produces a target compound having a fluoroalkyl group by reacting a starting compound (a material compound) which is an organic compound, with a fluoroalkylating agent.
(Fluoroalkyl) trialkylsilanes typified by (trifluoromethyl)trimethylsilane (Ruppert-Prakash reagent) are known as fluoroalkylating agents which have been conventionally used for fluoroalkylation reactions (see Non-Patent Document 1). Fluoroalkylation reactions using these fluoroalkylating agents are deduced to be nucleophilic reactions. In addition, these fluoroalkylating agents exhibit good reactivity. However, these fluoroalkylating agents require trifluoromethane (CHF3, HFC-23) of a greenhouse effect gas, or trifluoroiodomethane (CF3I) or bromotrifluoromethane (CBrF3) of Freon gas, as a material therefor. Therefore, these fluoroalkylating agents put a heavy load on the environment. Furthermore, these fluoroalkylating agents require an initiator such as fluorides in fluoroalkylation reactions. Furthermore, in a reaction with some starting compounds such as aldehydes, these fluoroalkylating agents have a problem that the temperature cannot be controlled because of exotherm.
With regard to the fluoroalkylation reactions, a reaction with trifluoromethane (CHF3) at low temperature is also known (see Non-Patent Document 2). However, there is a problem that this method requires trifluoromethane which is a greenhouse effect gas as described above.
Meanwhile, development of new products utilizing the compounds having a fluoroalkyl group has been carried out in various fields of biologically active substances, functional materials and others. In recent years, in order to meet demand thereof, various fluoroalkylating agents have been developed.
For example, as a fluoroalkylating agent, a fluoroalkyl phenyl sulfone compound is known (see Non-Patent Documents 3 and 4). The fluoroalkyl phenyl sulfone compound has been reported as an excellent fluoroalkylating agent for aldehydes, imines and the like. However, the reaction condition using the fluoroalkyl phenyl sulfone compound involves a low temperature of −70° C. to −30° C. Therefore, this fluoroalkylating agent is not industrially preferable because a special manufacturing facility is required.
It is known that, as another fluoroalkylating agent, the anhydrous salt obtained from hexafluoroacetone hydrate and 1,8-diazabicyclo[5.4.0]-7-undec-7-ene (DBU) reacts similarly to the fluoroalkyl phenyl sulfone compound described above (see Patent Document 3 and Non-Patent Document 5). In the reaction of this anhydrous salt, only one of the two fluoroalkyl groups which are contained in the same molecule of the anhydrous salt can be utilized for the reaction. Therefore, this method is inefficient. Furthermore, the method using this anhydrous salt requires a largely excessive amount of a quaternary ammonium salt and a low temperature. Therefore, this method is complicated.
As other fluoroalkylating agents, compounds having a fluoroalkyl group on their heteroatom such as sulfur or phosphorus have been reported. It is known that these compounds, i.e., fluoroalkylating agents also react similarly (Non-Patent Documents 6, 7 and 8). These fluoroalkylating agents can introduce a fluoroalkyl group into aldehydes or ketones under mild reaction conditions. However, the methods for the productions of these fluoroalkylating agents require the above-mentioned (trifluoromethyl)trimethylsilane (Ruppert-Prakash reagent), trifluoromethane (CHF3, HFC-23) of a greenhouse effect gas, or trifluoroiodomethane (CF3I) or bromotrifluoromethane (CBrF3) of Freon gas, as a material therefor. Therefore, these fluoroalkylating agents cannot substantially solve the problems.
As described above, the conventional fluoroalkylating agents depend heavily on a greenhouse effect gas (for example, CHF3) or Freon gas (for example, CF3I or CBrF3). In view of environmental aspects, development of the industrially usable fluoroalkylating agent has not yet been achieved satisfactorily.